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United States Department of Agriculture

Agricultural Research Service


item Rhoads, Marcia
item Fetterer, Raymond
item Romanowski, Robert - Bob

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: The stomach worm, Haemonchus contortus, is a blood feeding parasite that infests grazing ruminants causing disease and economic losses. Development of novel controls for parasitic nematodes can be enhanced by knowledge of the biochemical mechanism underlying the process of molting, an essential process in the growth and development of all nematodes. The results demonstrate that H. contortus produce an enzyme coincident with molting an differentiation. Inhibition of this enzyme activity may interfere with the molting process.

Technical Abstract: The trichostrongylid nematode, Haemonchus contortus, released a hyaluronic acid-degrading enzyme during in vitro development from the third to fourth larval stage. The enzyme did not degrade chondroitin sulfate A. Enzyme activity was optimal between pH 4.0 and 6.0, and the enzyme was inhibited by high concentrations of NaCl; the divalent cations Cu2+, Zn2+, Ca2+, and Mn2+ were not inhibitory. The hyaluronidase had a molecular weight estimated at 57 kDa by sucrose density gradient centrifugation and 111 kDa by substrate SDS-PAGE (reducing and non-reducing conditions), suggesting the formation of a dimer during the electrophoretic separation conditions. The level of hyaluronidase released during in vitro development peaked between 24 and 48 hr in culture and then gradually decreased, with little or no activity present in the 168-hr culture fluid. The enzyme was not detected in culture fluid from 24-hr incubations of either the mid-L4 stage e(obtained from sheep 7 days post-infection) or the adult stage (obtained from sheep 30-35 days post-infection). The temporal expression of the hyaluronidase suggested a role for this enzyme in the early stages of the L3 to L4 developmental process.

Last Modified: 06/26/2017
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